Quark deconfinement in compact stars: connection with GRBs Irene Parenti Univ. of Ferrara Italy INFN of Ferrara Italy International summer school: “Hot points in Astrophysics and Cosmology” Dubna, Russia 2 – 13 August 2004 August 2004 Irene Parenti

Summary Short overview on Gamma-Ray Bursts (GRBs) Delayed nucleation of Quark Matter Implication for the mass and radius of compact stars How to generate Gamma-Ray Bursts from deconfinement Conclusions August 2004 Irene Parenti

Gamma-Ray Bursts (GRBs) Spatial distribution: isotropic Distance: cosmological (1-10)∙109 ly Energy range: 100 KeV – a few MeV short GRBs few ms – 2 s long GRBs 2 s – few 100 s Emitted energy: 1051 erg (beamed/jets) Duration: (0,01-300) s J.S. Bloom, D.A. Frail, S.R. Kulkarni, ApJ 594, 2003 August 2004 Irene Parenti

GRB and supernovae Connection between GRB and Supernovae Evidence for atomic lines in the spectra of the X-ray afterglow time delay Δt between the Supernova explosion and the Gamma-Ray Burst. August 2004 Irene Parenti

Time delay from SN to GRB GRB 990705 ΔT ≈ 10 yr Amati et al., Science 290, 2000, 953 GRB 011211 ΔT ≈ 4 days Watson et al., ApJ 595, 2003, L29 GRB 030227 ΔT ≈ 3-80 days Reeves etal. , Nature 2002 August 2004 Irene Parenti

A two-stages scenario open questions 1st explosion: SUPERNOVA (birth of a NS) 2nd “explosion”: CENTRAL ENGINE OF THE GRB (ass. with the NS) What is the origin of the 2nd “explosion”? How to explain the long time delay between the two events? open questions August 2004 Irene Parenti

Delayed collapse of a HS to a QS Z. Berezhiani, I. Bombaci, A. Drago, F. Frontera and A. Lavagno ApJ. 586 (2003) 1250 Pure HS Hybrid Star or Quark Star Possible central engine for GRB The conversion process can be delayed due to the effects of the surface tension between the HM phase and the QM phase. The nucleation time depends drammatically on the central pressure of the HS. As a critical-size drop of QM is formed the HS is converted to a QS or a HyS. The conversion process releases: Econv. ≈ 1052 - 1053 erg A. Drago, A. Lavagno and G. Pagliara Phys. Rev. D69 (2004) 057505 when color superconductivity is taken in to account: August 2004 Irene Parenti

The Quark-Deconfinement Nova model August 2004 Irene Parenti

Finite-size effects quark-flavor must be conserved The formation of a critical-size drop of QM is not immediate. It’s necessary to have an overpressure to form a droplet having a size large enough to overcome the effect of the surface tension. A virtual droplet moves back and forth in the potential energy well on a time scale: ν0-1~10-23 s « τweak quark-flavor must be conserved during the deconfinement transition. August 2004 Irene Parenti

Quark deconfinement stable phase virtual droplet of deconfined quark matter real droplet of strange matter hadronic matter in a metastable state real droplet of deconfined quark matter stable phase This form of deconfined matter has the same flavor content of the β-stable hadronic system at the same pressure. We call it: Q*-phase. The drop grows with no limitation. in a time τ when p overcomes the transition point Soon afterwards the weak interactions change the quark flavor fraction to lower the energy. August 2004 Irene Parenti

Equation of State Hadronic phase: Relativistic Mean Field Theory of hadrons interacting via meson exch. [e.g. Glendenning, Moszkowsky, PRL 67(1991)] Quark phase: EOS based on the MIT bag model for hadrons. [Farhi, Jaffe, Phys. Rev. D46(1992)] Mixed phase: Gibbs construction for a multicom- ponent system with two conserved “charges”. [Glendenning, Phys. Rev. D46 (1992)] August 2004 Irene Parenti

Hybrid star: mass-radius B=136,36 MeV/fm3

Hybrid Star: configuration B=136,36 MeV/fm3

Strange Star: mass-radius B=74,16 MeV/fm3

Strange Star: configuration B=74,16 MeV/fm3

Quantum nucleation theory I.M. Lifshitz and Y. Kagan, Sov. Phys. JETP 35 (1972) 206 K. Iida and K. Sato, Phys. Rev. C58 (1998) 2538 Droplet potential energy: nQ* baryonic number density in the Q*-phase at a fixed pressure P. μQ*,μH chemical potentials at a fixed pressure P. σ surface tension (=10,30 MeV/fm2) August 2004 Irene Parenti

Matter in the droplet Flavor fractions are the same of the β-stable hadronic system at the same pressure: The pressure needed for phase transition is much larger than that without flavor conservation. August 2004 Irene Parenti

Nucleation time The nucleation time dramatically depends The nucleation time is the time needed to form a critical droplet of deconfined quark matter. It can be calculated for different values of the stellar central pressure (and then of the stellar mass, as implied by TOV). The nucleation time dramatically depends on the value of the stellar central pressure and then on the value of the stellar mass. August 2004 Irene Parenti

The critical mass of metastable HS We fixed the time of nucleation at 1 yr. The gravitational mass corresponding to this nucleation time is called critical mass: We assume that during the stellar conversion process the total numbers of baryons in the star (and then the baryonic mass) is conserved. [I. Bombaci and B. Datta, ApJ. 530 (2000) L69] The gravitational mass of the final star is taken to be the mass in the stable configu- ration corresponding to that baryonic mass. MHS < Mcr HS are metastable with a long mean-life time. MHS > Mcr This HS are very unlikely to be observed. August 2004 Irene Parenti

Two families of compact stars August 2004 Irene Parenti

Mass-Radius constraints X-ray burster EXO 0748-676 [Cottam et al., Nature 420, 2002] z=0.35 X-ray pulsar 1E 1207.4-5209 [Sanwal et al. ApJ 574, 2002, L61] z=0.12-0.23 X-ray binary 4U 1728-34 [Li et al. ApJ 527,1999,L51] Very compact object

Mass-Radius constraints

Energy released The total energy released in the stellar conversion is given by the difference between the gravitational mass of the initial hadronic star (Min=Mcr) and the mass of the final hybrid or strange stellar configuration (Mfin=MQS(Mbcr)): August 2004 Irene Parenti

How to generate GRBs The energy released is carried out by pairs of neutrinos – antineutrinos. The reaction that generate gamma-ray is: The efficence of this reaction in a strong gravitational field is: [J. D. Salmonson and J. R. Wilson, ApJ 545 (1999) 859] August 2004 Irene Parenti

Conclusions Neutron stars (HS) are metastable to HS ―> QS or to HS ―> HyS Econv ≈ 1052 – 1053 erg GRBs Our model explains the connection and the time delay between SN and GRBs. possible existence of two different families of compact stars: pure Hadronic Stars Hybrid stars or Strange Stars August 2004 Irene Parenti

Collaborators Dr. Ignazio Bombaci Dr. Isaac Vidaña Univ. of Pisa INFN of Pisa Ref: I. Bombaci, I. P., I. Vidaña arXiv:astro-ph/0402404 Astroph. J., accepted Other collaborators: Dr. Alessandro Drago Dr. Giuseppe Pagliara Univ. of Ferrara INFN of Ferrara August 2004 Irene Parenti

Appendix August 2004 Irene Parenti

Compact stars (HS) (HyS) HADRONIC STARS HYBRID STARS STRANGE STARS (SS or QS) conventional neutron stars hyperon stars August 2004 Irene Parenti

Probability of tunneling